Closure latch

ABSTRACT

A latch for a vehicle body closure, the latch including a latch bolt, a detent lever, means frictionally resisting movement of the detent lever and a transfer lever operable to overcome the friction and move the detent lever into and out of a detenting position against the latch bolt. A control pin on the latch bolt engages the transfer lever during movement of the latch bolt from an unlatched to a latched position to actuate the transfer lever and initiate simultaneous movement of the detent lever to the detenting position, the aforementioned friction functioning to maintain the detent lever in the detenting position.

United States Patent Meyer CLOSURE LATCH [72] Inventor: BartholdF.'Meyer, Mt. Clemens,

[58] Field of Search ..292/2l0, DIG. 24, DIG. 26, 292/280, 216, 198, 204

[56] References Cited UNITED STATES PATENTS 199,685 1/1878 Bergman..292/2l0 2,644,707 7/1953 Dall ..292/2l6 [451 Sept. 19, 1972 Pickles..292/280 Johnstone ..292/2l0 X [57] ABSTRACT A latch for a vehicle bodyclosure, the latch including a latch bolt, a detent lever, meansfrictionally resisting movement of the detent lever and a transfer leveroperable to overcome the friction and move the detent lever into and outof a detenting position against the latch bolt. A control pin on thelatch bolt engages the transfer lever during movement of the latch boltfrom an unlatched to a latched position to actuate the transfer leverand initiate simultaneous movement of the detent lever to the detentingposition, the aforementioned friction functioning to maintain the detentlever in the detenting position.

3 Claims, 7 Drawing figures PNENTEDSEP 1 9 m2 SHEET 1 0F 2 whowfii er 12.4%

A TORNEY PHENTEDSEHQ 1912 3.692.343

sum 2 UP 2 I NVENTOR.

BY 5arfho/d .51 Meyer ATTORNEY- CLOSURE LATCH This invention relatesgenerally to vehicle body closures and in particular to a positiveacting closure latch for releasably securing a vehicle body closure in aclosed position.

' A particular type of closure latch used extensively on automobiledoors is known to employ a bifurcated latch bolt for engaging andcapturing, in the closed position of the door, a striker rigidly mountedon the vehicle body. Typically, a cam or cam edge defining at least onedetent shoulder is rotatable as a unit with the latch bolt and isengaged by a detent lever which is constantly urged against the cam edgeso as to drop behind the detent shoulder when the latch bolt achieves alatched position thereby to prevent a reverse or unlatching movement ofthe latch bolt. Ordinarily, spring means are employed to constantly urgethe detent lever toward the detenting position behind the cam detentshoulder. This invention, however, substitutes for the usual detentlever and detent lever biasing spring an arrangement for mechanicallypositioning the detent lever in either the detenting or a releasingposition and means frictionally engaging the detent lever and preventingmovement thereof in the absence of an externally applied motivatingforce.

The primary feature of this invention is that it provides anew andimproved closure latch for a'vehicle body closure, the latch including alatch bolt engageable in a latched position on a striker and detentmeans operable in a detenting position to prevent unlatching movement ofthe latch bolt, the detent means being frictionally maintained in eitherthe detenting or in a releasing position. Another feature of thisinvention resides in the provision in the closure latch of detentcontrol means responsive to closing movement of the closure tomechanically position the detent means in detenting position in theclosed position of the closure. Yet another feature of this inventionresides in the provision in the closure latch of detent assist meansresponsive to closing movement of the closure to convert a portion ofthe kinetic energy thereof into potential energy, the latter beingselectively releasable to assist in moving the detent means from thedetenting to the releasing position. A still further feature of thisinvention resides in the provision in the closure latch of anintermediate transfer lever engageable with the detent means andcooperating in a detent operating or first functional mode with aprojection on the latch bolt to mechanically position the detent meansin the detenting position in response to movement of the latch bolt tothe latched position and cooperating in a release assist or secondfunctional mode with spring means to transfer to the latter forconversion to potential energy a portion of the kinetic energy of theclosure, the intermediate transfer lever thereafter being operable inresponse to release of the potential energy of the spring means to movethe detent means from the detenting to the releasing position.

These and other features of this invention will be readily apparent fromthe following specification and from the drawings wherein:

FIG. 1 is a fragmentary side elevational view of an automobile vehiclebody having a closure latch according to this invention;

FIG. 2 is an enlarged view taken generally along the plane indicated bylines 22 in FIG. 1 and showing the closure latch in unlatched condition;

FIG; 3 is a partially broken away view taken generally along the planeindicated by lines 3-3 in FIG. 2;

FIG. 4 is an exploded perspective view of the closure latch according tothis invention;

FIG. 5 is similar to FIG. 2 but showing the closure latch in fullylatched condition;

FIG. 6 is similar to FIG. 2 but showing thev closure latch inintennediate latched condition; and

FIG. 7 is similar to FIG. 5 but showing the intermediate transfer leverin position to initiate movement of the detent lever from the detentingto the releasing position.

Referring now to FIG. l-of the drawings, an automobile type vehicle bodygenerally designated 10 includes a right front fender structure 12, aright rear quarter panel structure 14 and a roof structure 16. The frontfender structure and rear quarter panel structure combine below thevehicle belt line 18 to define an access opening in the vehicle bodyadapted to be closed by a closure or front door 20 vertically hinged onthe vehicle body generally at the forward edge of the access opening forswinging movement between an open position, not shown, and a closedposition, FIG. 1. A striker 22 is rigidly secured to the rear jamb ofthe access opening and in the closed position of the door 20 is receivedwithin a closure latch 24 according to this invention mounted on door20.

With particular reference to'FIGS. 2 and 3 of the drawings, the closurelatch 24 includes a generally L- shaped base plate 26 having a short leg28 and long leg 30 with a striker clearance slot 32 formed therein. Thebase plate 26 is rigidly secured to the door 20 between inner and outerpanels thereof, not shown, with clearance slot 32 opening toward theinterior of the vehicle body in the closed position of the door andregistering with a similarly shaped aperture in the rear edge, notshown, of the door.

As best seen in FIGS. 2 and 4, a rivet 34 rigidly secured to long leg 30of the base plate 26 generally adjacent the clearance slot 32 rotatablysupports a bifurcated latch bolt 36 rigidly supporting a pair of spacedcontrol pins 44 and 4S and having a throat portion 38 and a cam edge 40defining a pairof detent shoulders 42 and 43. The latch bolt 36 isrotatable between an unlatched position, FIG. 2, and either anintermediate latched position, FIG. 6, or a fully latched position,FIGS. 5 and 7. A coil torsion spring, not shown, is supported on rivet34 with one end engaging the latch bolt 36 and the other end engagingthe base plate 26 to thereby bias the latch bolt counterclockwise towardthe unlatched position.

As best seen in FIG. 4, a detent lever 46 is provided to releasablymaintain the latch bolt in either of the intermediate and the fullylatched position, the detent lever having a circular aperture 48 thereinand including a detent leg 50, an upturned tab 52, and a stop projection53. A rivet or stud 56 of diameter generally equal to the diameter ofdetent lever aperture 48 is tightly received within the latter andmounts the detent lever on the base plate for rotary movement in a planegenerally parallel to long leg 30 of the base plate. Substantialfriction is generated between the shank of the rivet and the edge ofaperture 48, however, and effectively resists rotation of the detentlever in the absence of a significant motivating force applied to thelatter; In

the mounted position on rivet 56, the detent lever lies in generallyco-planar relation to the latch bolt 36 with stop projection 53 beingsituated between apair of spaced upturned tabs 57 on long leg 30 of thebase plate. The tabs 57 function to limit forced rotary movement of thedetent lever in a counterclockwise direction to a detenting position,FIGS. 5, 6 and 7, wherein detent 50 engages either one of detentshoulders 42 and 43 on the latch bolt and in a clockwise direction to areleasing position, FIG. 2, wherein detent 50 is remote from the latchbolt.

Referring now to FIGS. 2 and 4, the rivet 56 is freely received withinan elongated aperture 58 in an intermediate transfer lever 60 andsupports the transfer lever on the base plate .26 for pivotal movementand for bodily shiftable movement in a plane generally parallel to theplane of detent lever 46. The transfer lever 60 has integral therewith adownturned spring tab 62, a downturned driving tab 64, a downturnedlifting tab 66 and a depending leg 67 terminating in an upturned bearingtab 68. As best seen in FIGS. 2 and 5, the transfer lever 60 issupported on rivet 56 in overlying relation to detent lever 46v withlifting tab 66 underlying tab 52 on the detent lever, driving tab 64generally overlying the upper marginal edge of the detent lever anddepending leg 67 overlying latch bolt 36. The transfer lever isrotatable about the rivet 56 generally between a retracted position,FIG. 2, corresponding to the releasing position of the detent lever 46and an extended position, FIGS. and 6, corresponding to the detentingposition of the detent lever 46. A coil tension spring 70 has one endengaging spring tab 62 on the transfer lever 60 and the other endengaging a pin 72 projecting from long leg 30 of the base plate. Thespring 70 biases the transfer lever 60 clockwise toward the retractedposition thereof and resiliently maintains the upper edge of aperture 58in contact with the shank of rivet 56, FIG. 2.

Referring particularly now to FIGS. 2 and 4, a rivet 74 rigidlyprojecting from long leg 30 of the base plate is loosely received withina slot 76 in an operating lever 78 thereby supporting the latter on thebase plate for rotary and bodily shiftable movement in a plane parallelto the planes of the latch bolt 36 and the transfer lever 60. Theoperating lever 78 has a rigid lifting pin 82 projecting therefrom andin the mounted position of the operating lever on the rivet 74 thelifting pin underlies bearing tab 68 on the transfer lever while thedistal end of the operating lever protrudes through a slot 86 in theshort leg 28 of the base plate, FIG. 3.

Referring particularly now to FIGS. 1, 2 and 3, a simplified link andlever arrangement is shown for actuating the operating lever 78 andincludes an L-shaped lever 88 rotatably supported on short leg 28 of thebase plate at 90. One leg of the lever 88 underlies the distal end ofoperating lever 78 while the other leg thereof is connected to an insideoperating handle 92 bya draft link 94. A second draft link 96 has oneend pivotally connected to the first mentioned leg of lever 88 at 98 andthe other end operably connected to an exterior push button assembly100. Through the draft links 94 and 96, operation of either insidehandle 92 or push button assembly 100 functions to rotate the lever 88clockwise, FIG. 3, thus initiating clockwise pivotal movement, FIG. 2,of the operating lever 78 for a purpose to be described hereinafter.

When the door 20 assumes the open position, the latch bolt 36 normallyoccupies the unlatched position while the detent and the transfer levers46 and 60 assume the releasing and retracted positions, respectively,FIG. 2. Referring now to FIGS. 2 and 6, as the door 20 is brought towardclosed position, the latch bolt 36 engages the striker 22 in the throatportion of the former. As the bolt engages the striker, the kineticenergy or inertia of the closing door causes the striker to initiateclockwise rotary movement of the latch bolt bringing the control pin 45on'the latter into engagement with a side edge of depending leg 67 ofthe transfer lever. Subsequent to such engagement and upon continuedclockwise rotary movement of the latch bolt, the pin 45 initiatescounterclockwise rotary movement of the transfer lever 60 about rivet 56from the retracted position, FIG. 2, to the extended position, FIG. 6.Simultaneously, driving tab 64 -engages the upper edge of detent lever46 and initiates counterclockwise movement of the latter from thereleasing to the detenting position behind detent shoulder 43 on thelatch bolt when the latter achieves the intermediate latched position.The detent 50 thus maintains the latch bolt in the intermediate latchedposition, FIG. 6, while the detent lever 46 is positively maintained inthe detenting position by the aforementioned friction between the edgeof circular aperture 48 and the shank of rivet 56 and the transfer lever60 is held-in the extended position against spring by control pin 45 onthe latch bolt.

Normally, the kinetic energy of the closing door will be sufficient tocontinue rotary movement of the latch bolt beyond the intermediatelatched position to the fully latched position. Such movement of thelatch bolt initiates a second sequence of simultaneous movement of boththe detent lever and the transfer lever. First, referring to FIGS. 5 and6, as the latch bolt is rotated from the intermediate to the fullylatched position the detent 50 slides over the cam edge 40 of the latchbolt between the detent shoulders 42 and 43, the cam edge camming thedetent lever clockwise, FIG. 6, out of the detenting position againstthe friction at rivet 56. Simultaneously, the control pin 45 exerts anincreasing force on the side edge of depending leg 67, the latter forcebeing resisted by a force reaction between driving tab 64 and the upperedge of the detent lever at the point of contact therebetween. These twoopposing forces impose a counterclockwise force couple on the transferlever which rotates the transfer lever counterclockwise, FIG. 6, aboutthe point of engagement between driving tab 64 and the detent leveruntil the control pin 45 passes beneath the bearing tab 68, theaforementioned rotation being accommodated relative to the base plate 26by slot 58 in the transfer lever. As the control pin 45 passes beneaththe bearing tab, the spring 70 forces the upper end of slot 58 backagainst the rivet 56 while the second control pin 44 simultaneouslyengages the side edge of depending leg 67 of the transfer lever therebyinitiating counterclockwise rotation of the latter, FIGS. 5 and 6. Asthe latch bolt approaches the fully latched position, the control pin 44rotates the transfer lever to the extended position against spring 70while driving tab 64 on the transfer lever simultaneously rotates thedetent lever into the detenting position behind detent shoulder 42 onthe latch bolt when the latter achieves the fully latched position. Thedetent 50 thus maintains the latch bolt in the fully latched position,FIG. 5, while the detent lever 46 is positively maintained in thedetenting position by the aforementioned friction at rivet 56 and thetransfer lever 60 is held in the extended position against spring 70 bycontrol pin 44 on the latch bolt.

When release of the latch from either the fully or the intermediatelatched conditions is desired to permit opening movement of the door,either the door handle 92 or the push button assembly 100 is manuallyactuated to initiate clockwise rotation of the L-shaped lever 88, FIG.3. As the lever 88 rotates, the leg thereof underlying the operatinglever 78 contacts the latter and initiates clockwise rotation thereof,FIG. 5, bringing lifting pin 82 into engagement with the lower surfaceof bearing tab 78 on the transfer lever. The force exerted on transferlever 60 by lifting pin 82 is resisted by a force reaction between thetab 52 on the detent lever and the lifting tab 66 on the transfer lever.These two opposing forces impose a counterclockwise force couple, FIGS.5 and 6, on the transfer lever which rotates the latter counterclockwiseabout the point of contact between tab 52 and lifting tab 66 untilbearing tab 68 overlies control pin 44, FIG. 7. Immediately uponreaching this position, the restraint provided by the control pin isremoved from spring 70-and the latter rapidly rotates the transfer leverclockwise, FIG. 7, from the extended to the retracted position, thelifting tab 66 on the transfer lever simultaneously moving the detentlever from the detenting to the releasing position thereby to releasethe latch bolt for movement from either latched position to theunlatched position.

From the foregoing description, it will be apparent that the spring 70functions only to reduce the effort necessary to unlatch the door.Should failure of spring 70 occur while the detent lever 46 is in thedetenting position, the friction at the rivet 56 would permit no changein the position of the detent lever and the door would remain securelylatched. The only noticeable effect of the failure of spring 70 in thefully latched condition of the latch would be an increase in the effortrequired to unlatch the door. More particularly, with the 'spring 70inoperative, the motivating force for rotating the transfer lever anddetent lever out of the extended and the detenting positions,respectively, would have to be supplied directly by the lifting pin 82on the operating lever 78. Due to the requirement that the lifting pin82 now overcome the friction at rivet 56 in addition to lifting thebearing tab 68 over control pin 44, an increased effort at the pushbutton 100 or handle 92 is necessary. This increased effort will, ofcourse, be apparent to the operator and indicate to him that repair ofthe latch is necessary. Should the spring 70 fail while the latch is inthe unlatched condition, closing movement of the door would initiate thenormal latching sequence as described hereinbefore. Thus, it is apparentthat the closure latch according to this invention remains fullyoperative regardless of the condition of the spring 70.

Finally, the latch is provided with a simplified arrangement forpreventing unauthorized manipulation. More particularly, as best seen inFIGS. 1 and 5, conventional link and lever means, not shown, arearranged between an interior garnish button 102 and an exterior lockcylinder 104 and the operating lever 78.

When either the garnish button or lock cylinder is actuated,.the linkand lever means function to bodily shift the operating lever leftwardly,FIG. 5, to a location, not shown, wherein the lifting pin no longerunderlies the bearing tab 68 on the transfer lever so-that actuation ofhandle 92 or push button assembly results merely in freewheelingmovement of the lifting pin past the bearing tab 68 and along side ofdepending leg 67.

Having thus described the invention, what is claimed 1. In a vehicleincluding a body member having an opening therein and a striker rigidlysecured to one of said body member and a closure mounted thereon formovement between open and closed positions relative to said opening, aclosure latch comprising a latch bolt, means mounting said latch bolt onthe other of said body member and said closure for movement between alatched position capturing said striker in said closed position of saidclosure and an unlatched position releasing said striker, said latchbolt in said latched position thereof retaining said closure in saidclosed position, detent means movable between a detenting positionengaging said latch bolt in said latched position of the latter andpreventingmovement thereof towards said unlatched position and areleasing position remote from said latch bolt, friction means remotefrom said latch bolt frictionally engaging said detent means, saidfriction means being the sole means for maintaining said detent means ineither of said detenting and said releasing positions, detent operatingmeans responsive to movement of said latch bolt from said unlatched tosaid latched position to overcome said friction means and forcibly movesaid detent means from said releasing to said detenting position, anddetent release means selectively operable to overcome said frictionmeans and move said detent means from said detenting to said releasingposition thereby to release said latch bolt for movement from saidlatched to said unlatched position thereof.

2. In a vehicle including a body member having an opening therein and astriker rigidly secured to one of said body member and a closure mountedthereon for movement between open and closed positions relative to saidopening, a closure latch comprising a bifurcated latch bolt, meansmounting said latch bolt on the other of said body member and saidclosure for pivotal movement between a latched position capturing saidstriker in said closed position of said closure and an unlatchedposition releasing said striker, said latch bolt in said latchedposition thereof retaining said closure in said closed position, adetent lever, means mounting said detent lever on said other of saidbody member and said closure for movement between a detenting positionengaging said latch bolt and maintaining the latter in said latchedposition and a releasing position remote from said latch bolt, frictionmeans remote from said latch bolt frictionally engaging said detentlever, said friction means being the sole means for maintaining saiddetent lever in either of said detenting and said releasing positions,an intermediate transfer lever, means mounting said intermediatetransfer lever on said other of said body member and said closure formovement between extended and retracted positions, said intermediatetransfer lever being engageable on said detent lever and being operableupon movement from said retracted to said extended position to overcomesaid friction means and move said detent lever from said releasing tosaid detenting position and upon movement from said extended to saidretracted position being operable to overcome said friction means andmove said detent lever from said detenting to said releasing position,means on said latch bolt and on said intermediate transfer leverresponsive to movement of said latch bolt from said unlatched to saidlatched position to move said transfer lever from said retracted to saidextended position, and release means selectively operable to move saidtransfer lever from said extended to said retracted position thereby tosimultaneously move said detent lever from said detenting to saidreleasing position to release said latch bolt for movement from saidlatched to said unlatched position.

3. In a vehicle including a body member having an opening therein and astriker rigidly secured to one of said body member and a closure mountedthereon for movement between open and closed positions relative to saidopening, a closure latch comprising a bifurcated latch bolt, meansmounting said latch bolt on the other of said body member and saidclosure for pivotal movement between a latched position capturing saidstriker in said closed position of said closure and an unlatchedposition releasing said striker, said latch bolt in said latchedposition thereof retaining said closure in said closed position, adetent lever mounted on said other of said body member and said closurefor movement between a detenting position engaging said latch bolt andmaintaining the latter in said latched position and a releasing positionremote from said latch bolt, friction means remote from said latch boltfrictionally engaging said detent lever, said friction means being thesole means for maintaining said detent lever in either of said detentingand said releasing positions, an intermediate transfer lever, meansmounting said intermediate transfer lever on said other of said bodymember and said closure for movement between extended and retractedpositions, said intermediate transfer lever being engageable on saiddetent lever and being operable upon movement from said retracted tosaid extended position to overcome said friction means and move saiddetent lever from said releasing to said detenting position and uponmovement from said extended to said retracted position being operable toovercome said friction means and move said detent lever from saiddetenting to said releasing position, spring means biasing saidintermediate transfer lever toward said retracted position thereof, acontrol projection rigidly secured to said latch bolt and engageable onsaid intermediate transfer lever during movement of said latch bolt fromsaid unlatched to said latched position, said projection thereafterforcibly rotating said transfer lever against said spring means fromsaid retracted to said extended position thereby to position said detentlever in said detenting position, and means selectively operable in saidextended position of said transfer lever to disengage the latter fromsaid control projection thereby to permit said spring means tomove saidtransfer lever from said extended to said retracted position, saidtransfer lever simultaneously moving said detent lever from saiddetenting to said releasing position thereby to release said latch boltfor movement from said latched to said unlatched position.

=0 t I! I

1. In a vehicle including a body member having an opening therein and astriker rigidly secured to one of said body member and a closure mountedthereon for movement between open and closed positions relative to saidopening, a closure latch comprising a latch bolt, means mounting saidlatch bolt on the other of said body member and said closure formovement between a latched position capturing said striker in saidclosed position of said closure and an unlatched position releasing saidstriker, said latch bolt in said latched position thereof retaining saidclosure in said closed position, detent means movable between adetenting position engaging said latch bolt in said latched position ofthe latter and preventing movement thereof towards said unlatchedposition and a releasing position remote from said latch bolt, frictionmeans remote from said latch bolt frictionally engaging said detentmeans, said friction meaNs being the sole means for maintaining saiddetent means in either of said detenting and said releasing positions,detent operating means responsive to movement of said latch bolt fromsaid unlatched to said latched position to overcome said friction meansand forcibly move said detent means from said releasing to saiddetenting position, and detent release means selectively operable toovercome said friction means and move said detent means from saiddetenting to said releasing position thereby to release said latch boltfor movement from said latched to said unlatched position thereof.
 2. Ina vehicle including a body member having an opening therein and astriker rigidly secured to one of said body member and a closure mountedthereon for movement between open and closed positions relative to saidopening, a closure latch comprising a bifurcated latch bolt, meansmounting said latch bolt on the other of said body member and saidclosure for pivotal movement between a latched position capturing saidstriker in said closed position of said closure and an unlatchedposition releasing said striker, said latch bolt in said latchedposition thereof retaining said closure in said closed position, adetent lever, means mounting said detent lever on said other of saidbody member and said closure for movement between a detenting positionengaging said latch bolt and maintaining the latter in said latchedposition and a releasing position remote from said latch bolt, frictionmeans remote from said latch bolt frictionally engaging said detentlever, said friction means being the sole means for maintaining saiddetent lever in either of said detenting and said releasing positions,an intermediate transfer lever, means mounting said intermediatetransfer lever on said other of said body member and said closure formovement between extended and retracted positions, said intermediatetransfer lever being engageable on said detent lever and being operableupon movement from said retracted to said extended position to overcomesaid friction means and move said detent lever from said releasing tosaid detenting position and upon movement from said extended to saidretracted position being operable to overcome said friction means andmove said detent lever from said detenting to said releasing position,means on said latch bolt and on said intermediate transfer leverresponsive to movement of said latch bolt from said unlatched to saidlatched position to move said transfer lever from said retracted to saidextended position, and release means selectively operable to move saidtransfer lever from said extended to said retracted position thereby tosimultaneously move said detent lever from said detenting to saidreleasing position to release said latch bolt for movement from saidlatched to said unlatched position.
 3. In a vehicle including a bodymember having an opening therein and a striker rigidly secured to one ofsaid body member and a closure mounted thereon for movement between openand closed positions relative to said opening, a closure latchcomprising a bifurcated latch bolt, means mounting said latch bolt onthe other of said body member and said closure for pivotal movementbetween a latched position capturing said striker in said closedposition of said closure and an unlatched position releasing saidstriker, said latch bolt in said latched position thereof retaining saidclosure in said closed position, a detent lever mounted on said other ofsaid body member and said closure for movement between a detentingposition engaging said latch bolt and maintaining the latter in saidlatched position and a releasing position remote from said latch bolt,friction means remote from said latch bolt frictionally engaging saiddetent lever, said friction means being the sole means for maintainingsaid detent lever in either of said detenting and said releasingpositions, an intermediate transfer lever, means mounting saidintermediate transfer lever on said other of said body meMber and saidclosure for movement between extended and retracted positions, saidintermediate transfer lever being engageable on said detent lever andbeing operable upon movement from said retracted to said extendedposition to overcome said friction means and move said detent lever fromsaid releasing to said detenting position and upon movement from saidextended to said retracted position being operable to overcome saidfriction means and move said detent lever from said detenting to saidreleasing position, spring means biasing said intermediate transferlever toward said retracted position thereof, a control projectionrigidly secured to said latch bolt and engageable on said intermediatetransfer lever during movement of said latch bolt from said unlatched tosaid latched position, said projection thereafter forcibly rotating saidtransfer lever against said spring means from said retracted to saidextended position thereby to position said detent lever in saiddetenting position, and means selectively operable in said extendedposition of said transfer lever to disengage the latter from saidcontrol projection thereby to permit said spring means to move saidtransfer lever from said extended to said retracted position, saidtransfer lever simultaneously moving said detent lever from saiddetenting to said releasing position thereby to release said latch boltfor movement from said latched to said unlatched position.